1. Field of the Invention
The present invention relates to an earphone, and more particularly, to the one that has two speaker units.
2. Description of Related Art
With the rapid progress in science and technology, all electronic products have been developed towards light, handy and miniaturized designs. People may use miniaturized electronic products, such as radios or walkmans, anytime and anywhere. Moreover, the personal digital product, such as common MP3 walkmans, cell phones, personal digital assistants (PDAs) or notebooks, has increasingly become popular, and thus being indispensable in the daily life. In addition, the cell phone integrated with functions of both radio and MP3 has immerged.
For each of those aforementioned electronic products, in order to allow a user to listen to the audio information provided by the electronic product without disturbing the other people around, an earphone has become a necessary accessory to the electronic product. Moreover, the earphone also provides a listener better audio transmission so that the listener can clearly hear and understand content of the audio information. In contrast to unclear audio transmission through the air, especially when the listener is moving, for example like doing exercises, driving, intensely moving around or being in a noisy environment, the audio transmission of the earphone still would not be affected.
The conventional earphone generally uses a single speaker unit. However, the output audio frequency of each speaker unit has specific range, and uniform performance in all frequency can not be achieved.